When a disease causing organism passes from an animal to a human, scientists refer to it as a zoonosis. Rabies is a familiar zoonotic infection and is most often caused by an animal bite that introduces the virus into a person’s body. Rabies infections cause nearly 100% mortality in humans and bites by suspect animals require immediate medical attention. Because of the deadly nature of the disease, great measures are taken in the United States to vaccinate pets against the disease. The virus that causes rabies can be found in a number of wild mammals but raccoons, skunks, and bats are most commonly found to be carriers.
Our greatest protection against zoonosis, vaccination, ironically gets its name from the zoonotic disease Cowpox which is caused by the Vaccinia virus. During the 1700’s, doctors noticed that milkmaids that had acquired cowpox from their milk cows seemed to be immune to the smallpox outbreak that was sweeping much of Europe. Experiments (often on family members!) showed that infecting people with cowpox did infer immunity to smallpox in the future. These experiments inspired scientists to develop vaccines for hundreds of diseases. Zoonotic infections that ravaged human populations for centuries have now been nearly eradicated. However, some infectious organisms have not been stopped by vaccines. Cholera and Malaria still cause a great deal of death and suffering especially in the developing world. Outbreaks of Ebola and Avian influenza (Bird Flu) are cause for alarm and are closely tracked by scientists.
If you would like to learn more about zoonotic infections and animals, you can check out the Center for Disease Control’s Healty Pets Healthy People website.
I’ve just been watching the (very good) HBO miniseries John Adams, and there is one squeamish scene showing Abigail Adams and kids recieving the “new” and risky vaccination procedure for the pox. I am glad to live in 2009 with syringes and needles– the old vaccination methods were really scary!!